(CNN) — The U.S. Supreme Court on Tuesday upheld Michigan’s voter-approved law that bans use of racial criteria in college admissions.

In a 6-2 vote, the court ruled a lower court did not have the authority to set aside the law.

The law passed in a 2006 referendum, supported by 58% of voters. It bars publicly funded colleges from granting “preferential treatment to any individual or group on the basis of race, sex, color, ethnicity or national origin.”

That prompted a series of lawsuits and appeals from a coalition of civil rights groups and University of Michigan faculty and students, who countered that the law denied them the opportunity to persuade state and college officials that classroom and workplace diversity remains a necessary government role.

A federal appeals court last year concluded the affirmative action ban violated the U.S. Constitution’s equal protection guarantees.